as C.Steinbach mentioned there’s a javascript library that helps you perform the transformation you’re aiming for.
However i suggest putting the connector call inside a server side business object method and transform the data inside the methode. This way there’s only one shape inside the process designer and the data will always be formatted without the need of an additional script shape.
After adding the connector to the business object you can access the call using the business object API. After loading the data you can use moment.js to format as already mentioned by C.Steinbach.
